So I'm not sure how feasible this is, but I figured "if there was any way to make this possible, it would have to be at an event like ESA".

You may not know this, but Double Dash has support for more than 4 players. Problem is, it's crazy to set everything up.

The worst aspect has got to be these pesky, ever-elusive broadband adapters that nobody seems to own. Well, it just so happens that I have 8 of them and they all work, so that's not gonna be the issue here.

It's too early to celebrate though. You still need a bunch of Gamecubes (NOT Wiis, the broadband adapter doesn't fit anywhere), Controllers, Double Dash Discs (I don't think different game regions are compatible btw), TV's, an Ethernet HUB and some LAN cables.

The most luxurious setup is this: 8 TV's, discs, Gamecubes etc. for 16 players. Each TV has a team of 2 players for each kart (remember that this is Double Dash with 2 Characters per kart).

Even for ESA, this may be too ambitious. In that case, the next option is to cut all of these above numbers in half. 4 Gamecubes still provide 16 controller ports for 16 players. It's just that each TV will be occupied by 4 people instead of 2 with splitscreen action. Sounds like a reasonable compromise.

The most minimalistic setup would be only 2 Gamecubes and 2 TV's for 8 players (with 4-way splitscreen on each TV). Here you don't need a HUB, just a single "crossover" cable.

Well, what say you? Does anyone have experience organising something like this? Is it feasible to gather all the equipment and set everything up on-site? What setup should we strive for?

And most importantly: Do you guys even WANT this or are you guys like, nah I'm good.

Hey guys, I wonder if we can set this up again like we did last year? The reception from all players and contributors was overwhelmingly positive and so I'd love to try again. 

If you're new to this, here's the deal (also last year's thread https://www.speedrun.com/esa2017/thread/cnvee )

Mario Kart Double Dash can be played with far more than 4 players (up to 16 in fact if every kart gets controlled by 2 players). The setup is seriously complicated and intricate though, so most of the time it can't really be done.
Usually, one of the main reasons these LAN events can't take place is because no one has enough (or any) Broadband Adapters. But I've got more of them than anyone should ever see in one lifetime, so that's a big hurdle out of the way from the get-go.

Here's the list of all the things we'd need:

Up to 8 Broadband Adapters (I've got em all so no need to worry about this one)
Up to 16 Gamecube Controllers (so ANY controller you can contribute greatly helps)
Up to 8 Gamecubes (we don't *need* the maximum 8 but we should aim for it like last time)
Up to 8 Double Dash Discs (see above) 
Up to 8 Ethernet Cables (we got them on-site really easily last time and I assume this time will be the same)
One switch with 8 Ethernet ports (you plug the ethernet cables in there and the consoles get linked)

I myself plan to bring along the adapters, 4 controllers, 1 Gamecube and 4 game discs.

If you can contribute anything, even just one console or just one controller, it would really help out a lot. Thanks!

During the Mario Kart Double Dash LAN, I connected my LAN adapters with many Gamecubes that aren't mine. Unfortunately, it seems like one person at some point took their Gamecube back and did not remove the adapter, taking it home with them.
If you brought your Gameube to ESA, I'd like to ask you to check the bottom of it. You should immediately see the adapter plugged in if it's actually there. It should have a sticker with my name printed on it as well, but it's also possible it has since fallen off. It can really only be mine though because only one other person brought another adapter and they definitely took theirs with them.
There is no doubt I didn't lose the adapter myself before/at ESA because we gathered all 8 together at one point and played with them.

If you know anything or you are the person who took the adapter by accident, please reply in this thread or message me on Twitter or Discord or whatever you want. Thanks!

EDIT: Forgot to mention that we found a black cover for the port the adapter goes into where the LAN was held. So in all likelihood the Gamecube in question is a black one. Should also pretty much confirm the theory of how it went missing.